spring-: logical-execution-order-and-code-flow

This diagram illustrates the step-by-step execution flow and bean lifecycle within a Spring application. Let's break down the process:

Phase 1: Application Context Initialization

The application starts by creating a Spring AnnotationConfigApplicationContext using TenantConfig as the configuration source. This triggers Spring's bean discovery and initialization process.

Phase 2: Bean Definition and Scanning

TenantConfig, annotated with @Configuration, defines two beans: tenantA-dataSource and tenantB-dataSource, both instances of TenantDataSource. The @ComponentScan annotation instructs Spring to scan the org.example4 package for components, discovering and registering TenantService (due to its @Service annotation).

Phase 3: Bean Creation and Dependency Injection

Spring now instantiates the TenantDataSource beans. Crucially, TenantDataSource implements BeanNameAware. This interface's setBeanName() method is called by Spring, allowing each TenantDataSource instance to dynamically determine its tenant name (e.g., "tenantA" or "tenantB") and configure its database URL accordingly.

Next, Spring creates the TenantService bean. The @Autowired annotation on the constructor, combined with @Qualifier annotations, ensures that the correct TenantDataSource instances are injected as dependencies. This is constructor-based dependency injection.

Phase 4: Bean Retrieval and Method Execution

The main method retrieves the fully configured TenantService bean from the application context using context.getBean(TenantService.class). Finally, tenantService.processTenantData() is called. This method utilizes the injected TenantDataSource beans to connect to the respective databases ("tenantA_db" and "tenantB_db"), demonstrating the successful dependency injection and bean lifecycle management.

Key Concepts Highlighted:

• Dependency Injection (DI): Spring injects the necessary dependencies (TenantDataSource instances) into TenantService automatically.
• Bean Lifecycle: The BeanNameAware interface showcases a specific point in the bean lifecycle where beans can react to their assigned name.
• @Configuration and @ComponentScan: These annotations are central to Spring's configuration mechanism, defining beans and scanning for components.
• @Autowired and @Qualifier: These annotations control dependency injection, ensuring correct bean wiring.
• IoC Container: The Spring application context acts as the IoC (Inversion of Control) container, managing the entire lifecycle of beans.

This detailed explanation and the visual diagram provide a clear understanding of the Spring bean initialization process, focusing on dependency injection and the bean lifecycle.

The above is the detailed content of spring-: logical-execution-order-and-code-flow. For more information, please follow other related articles on the PHP Chinese website!